Big time cost!! A 12,000btu Mitsubishi mini split will cost upwards of $2,000. The size of the condensing unit would be a factor as well. I have yet to see a condenser shorter than the current units on RV's. Now, I'm not saying you couldn't adapt one to an RV. But where are you going to mount all the components?
Mini splits are nice but in my opinion, not for RV's. Unless the minisplit manufacturers design one specifically for RV's, I don't see any of them working out.
2015 Jayco 24FBS Elite Jay Flight
2013 Chevrolet Silverado 2500HD 4X4 6.0L 3.73 Axle
HD Trailering Package with Integrated Brake Controller
Equal-i-zer Hitch 10k/1000